Open-Ear Acoustic Output Structure for High-Frequency Leakage Control
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Solution Overview
Problem
Open acoustic output devices suffer from unsatisfactory sound leakage reduction in high-frequency bands due to phase interference between sound emitted from different chambers, despite effective cancellation in low-frequency bands.
Innovation Solution
The device employs two speakers generating sound in different frequency bands, with specific resonance frequencies and sound guiding holes to cancel sound leakage in the far field, particularly for frequencies between 3 kHz and 6 kHz, using a housing structure that positions near the ear canal without blocking it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If sound with opposite phases is output from sound guiding hole and pressure relief hole to cancel sound leakage, then far-field sound leakage is reduced in low-frequency bands, but phase interference occurs in high-frequency bands causing unsatisfactory sound leakage reduction
Solution Approach 1:
The patent divides the acoustic output device into two separate acoustic systems: a first acoustic system (speaker + front chamber + sound guiding hole) for low-frequency sound output and a second acoustic system (driver + rear chamber + pressure relief hole) for high-frequency sound output. This segmentation allows each system to be optimized for its specific frequency band, resolving the phase interference problem that occurs when a single system attempts to handle both frequencies.
Solution Approach 2:
The patent applies different acoustic characteristics to different parts of the device: the front chamber is designed with a larger volume and sound guiding hole configuration optimized for low-frequency sound radiation, while the rear chamber is designed with a smaller volume and pressure relief hole configuration optimized for high-frequency sound radiation. This local quality differentiation ensures that each chamber-sound hole combination effectively handles its designated frequency range without causing phase interference.
2Ease of operation
If open acoustic output device structure is used, then comfort and ambient sound awareness are improved, but sound leakage to surrounding environment increases
Solution Approach 1:
The patent segments the sound radiation function across two separate acoustic systems with different frequency responsibilities. The open acoustic structure is maintained for comfort, while the segmented frequency handling allows effective sound leakage cancellation in the far field through phase opposition between the two systems.
Solution Approach 2:
The patent changes the acoustic parameters of the two chambers differently: the front chamber is designed with larger volume and appropriate sound guiding hole area for low-frequency resonance, while the rear chamber is designed with smaller volume and appropriate pressure relief hole area for high-frequency resonance. This parameter differentiation enables frequency-specific sound leakage control while maintaining the open structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces sound leakage in high-frequency bands by phase cancellation and directs sound primarily towards the ear canal, maintaining comfort and clarity for both ambient and device sounds.
Implementation Method 1
a first speaker including a first diaphragm configured to generate sound in a first frequency band
Implementation Method 2
a second speaker including a second diaphragm configured to generate sound in a second frequency band
Implementation Method 3
The front chamber has a first resonance frequency. The rear chamber has a second resonance frequency
Implementation Method 4
sounds with opposite phases may be output from a sound guiding hole of a front chamber and a pressure relief hole of a rear chamber... the sounds can cancel each other out, thereby reducing sound leakage in the far field
Data Source
AI summary
An acoustic output device is provided. The acoustic output device includes: a first speaker, a second speaker, a housing, and a support structure. The first speaker includes a first diaphragm configured to generate sound in a first frequency band. The second speaker includes a second diaphragm configured to generate sound in a second frequency band. The second frequency band includes frequencies higher than an upper limit frequency of the first frequency band. The housing is configured to carry the first speaker and the second speaker. The support structure is configured to place the housing near an ear canal without blocking an entrance of the ear canal. At least two sound guiding holes are disposed on the housing. A first sound guiding hole of the at least two sound guiding holes is acoustically coupled to a front side of the first diaphragm and defines a front chamber of the first speaker. A second sound guiding hole of the at least two sound guiding holes is acoustically coupled to a rear side of the first diaphragm and defines a rear chamber of the first speaker. The front chamber has a first resonance frequency. The rear chamber has a second resonance frequency. A higher one of the first resonance frequency and the second resonance frequency is in a range of 3 kHz to 6 kHz.